I think you already know whats about to happen! 'All Guardians stand alert! Report to your class master now! There has been a breach in the wall!'
9 guardians (max. 3 per fireteam) vs. An army (5000-10000 units) of attacking Fallen/Hive. With the new subclasses coming and awesome new gear, 9 guardians will defend the Tower from invading Fallen/Hive.
This is an event like Iron Banner. It could happen anytime, it has a time duration 3 days and in those 3 days it could happen just once or multiple times. The intire 3 days could even happen twice a week or just once a month.
The enemies will come in waves of 100-1000 enemies each wave has a timer, so when you are too late the next legion will come!
The way the loot system works is that you will get (per wave) a loot boon/buff where engrams drop faster and sometimes there will be an exotic drop!
Feel free to give constructive criticism.
-
Why the hell would they bother breaching the wall? They have ships! Hell the hive can rip a hole in reality and go wherever they damn well please. Not saying I don't like this idea, just has some [b]logic[/b] holes. Plug those, and you are golden.